During the coming year we will investigate the factors that permit hexosediphosphatase and phosphofructokinase to be simultaneously active in the muscle of halothane-susceptible swine under conditions where these two enzymes are reciprocally controlled and where their activities are mutually exclusive in the muscle of normal swine. To this end we will continue to alter, with specific reagents, the normal enzyme and will try to achieve conditions under which the isolated enzyme will respond directly to halothane. The interaction of such effectors as calcium, potassium, magnesium, adenosine monophosphate, fructose 6- phosphate, and fructosediphosphate with the enzyme in the presence and absence of halothane will be investigated. We will also continue to study the possible relationship of the hyperthermia induced by excessive amounts of thyroid hormones to the thermogenic metabolic cycles that occur in the pathways for carbohydrate metabolism, and will continue to investigate the reasons for our inability to detect an enhanced activity of the sodium-potassium pump in the liver and other tissues of animals treated with metabolically stimulating doses of triiodothryonine.